What are the flue gas purification equipment for lime vertical kilns
Lime vertical kilns produce a large amount of flue gas containing various pollutants during the production process. If these flue gases are directly discharged into the atmosphere, they will cause serious harm to the environment and human health. Therefore, appropriate flue gas purification equipment must be used to treat these flue gases in order to meet environmental emission standards.
1、 Dust removal equipment
（1） Bag filter
Bag filter is a commonly used high-efficiency dust removal equipment. Its working principle is that when the dusty gas passes through the filter bag, the dust is blocked on the outer surface of the filter bag, and the purified gas is discharged from the inside of the filter bag. For dust in the flue gas of lime vertical kilns, bag filters have high dust removal efficiency, generally reaching over 99%. Its filter bag material is usually made of high temperature resistant and corrosion-resistant materials to adapt to the high temperature and chemical characteristics of lime vertical kiln flue gas. The bag filter has a relatively simple structure and stable operation, but it requires regular cleaning operations to ensure its dust removal effect.
（2） Electrostatic precipitator
The electrostatic precipitator uses a high-voltage electric field to charge the dust in the flue gas, and then under the action of the electric field force, the dust moves towards the electrode and is captured. It is suitable for processing large amounts of flue gas with high temperatures. The electrostatic precipitator has a certain selectivity for dust particle size and has a good capture effect on fine particles. In the purification of flue gas in lime vertical kilns, electrostatic precipitators can effectively remove most of the dust in the flue gas. However, the equipment investment for electrostatic precipitators is relatively large, and there are high technical requirements for operation and maintenance.
2、 Desulfurization equipment
（1） Wet desulfurization equipment
Lime gypsum desulfurization device: This is a common wet desulfurization technology. It reacts lime slurry with sulfur dioxide in flue gas to produce calcium sulfite, which is then further oxidized into calcium sulfate (gypsum). The device mainly includes absorption tower, slurry circulation pump, oxidation fan and other equipment. The absorption tower is the core component, and the flue gas fully contacts with the sprayed lime slurry inside the absorption tower to achieve desulfurization process. The slurry circulation pump ensures the circulation and spraying of the slurry, improving the desulfurization efficiency. The oxidation fan oxidizes calcium sulfite to calcium sulfate.
Double alkali desulfurization device: The double alkali method uses sodium hydroxide or sodium carbonate solution as the absorbent, and the solution after absorbing sulfur dioxide is regenerated with lime. It has the advantages of high desulfurization efficiency and low fouling. Its equipment composition is similar to the lime gypsum method, but there are differences in the specific process flow and operating parameters.
（2） Dry desulfurization equipment
Dry desulfurization generally uses powdered or granular desulfurizers, such as lime powder, sodium bicarbonate, etc. The commonly used dry desulfurization equipment in lime vertical kiln flue gas purification is the dry desulfurization tower. The flue gas enters from the bottom of the desulfurization tower and reacts thoroughly with the desulfurizer sprayed from the top of the tower to remove sulfur dioxide. The advantages of dry desulfurization equipment are simple process flow, no wastewater generation, and small equipment footprint. But its desulfurization efficiency is slightly lower compared to wet desulfurization.
3、 Denitrification equipment
（1） Selective Catalytic Reduction (SCR) Denitrification Equipment
SCR denitrification equipment is currently a widely used denitrification technology. It reacts ammonia with nitrogen oxides in flue gas under the action of a catalyst, generating nitrogen gas and water. SCR denitrification equipment mainly includes denitrification reactors, catalysts, ammonia injection systems, etc. The denitrification reactor is the site of denitrification reaction, and the catalyst is a key component that can accelerate the reaction. The ammonia injection system requires precise control of the amount of ammonia injected to ensure denitrification efficiency and avoid secondary pollution caused by excessive ammonia. The denitrification efficiency of SCR denitrification equipment is relatively high, generally reaching over 80%.
（2） Selective Non Catalytic Reduction (SNCR) Denitrification Equipment
SNCR denitrification equipment sprays reducing agents containing amino groups (such as ammonia water, urea solution, etc.) into the furnace without the need for catalysts, and reacts with nitrogen oxides. Its equipment is relatively simple and the investment cost is low. But the denitrification efficiency is relatively low compared to SCR, generally between 30% and 70%. In the flue gas purification of lime vertical kilns, SNCR denitrification equipment can be used as a supplement or under specific conditions.
4、 Other auxiliary equipment
（1） Induced draft fan
The induced draft fan is used to introduce the flue gas generated by the lime vertical kiln into the purification system and overcome the resistance of the entire system, so that the flue gas can smoothly pass through various purification equipment. It needs to be selected reasonably based on parameters such as flue gas flow rate and pressure to ensure the normal operation of the system.
（2） Chimney
Chimneys are channels for smoke emissions. It not only needs to meet certain height requirements to ensure effective diffusion of smoke and reduce its impact on the surrounding environment, but also needs to have good anti-corrosion, insulation and other properties.
（3） Online monitoring equipment
Online monitoring equipment is used for real-time monitoring of various parameters before and after flue gas purification, such as flue gas flow rate, temperature, pressure, pollutant concentration, etc. Through these data, operators can timely understand the operation of the purification system, adjust equipment operating parameters, and ensure that the purification effect meets environmental standards.
The purification of flue gas in lime vertical kilns requires multiple devices to work together. Dust removal equipment removes dust from flue gas, desulfurization equipment reduces sulfur dioxide emissions, denitrification equipment reduces nitrogen oxide content, and auxiliary equipment ensures the normal operation of the entire purification system and the compliance of flue gas emissions. Different devices have their own characteristics and applicability. In practical applications, it is necessary to make reasonable choices and configurations based on the specific situation of the lime vertical kiln to achieve efficient and stable flue gas purification effects, protect the environment and human health.
